The 2008 financial crisis has provoked widespread interest in developing new taxes to apply to the financial sector. In particular, the Staff of the International Monetary Fund has suggested enactment of a financial activities tax (FAT), while the European Commission has proposed a financial transactions tax (FTT). This article discusses the FAT and FTT models that have featured in historical and more recent discussion, and evaluates them in light of the objectives stated by the European Commission, along with broader tax policy considerations. It concludes that there is a strong case for enacting an FAT, and that two alternative versions of this tax have competing pluses and minuses. With respect to the FTT, it concludes that the rationales advanced by the European Commission are unpersuasive, but that an argument could perhaps made for the tax – subject to concern about its clear inefficiency at certain margins – based on the goal of discouraging the socially excessive pursuit of trading profits (or if better instruments for raising revenue and increasing progressivity are politically unavailable).